Method, system and apparatus for low-power storage of processor context information

Abstract

A method and system for saving and/or retrieving context information of a processor core for a power state transition. The processor core resides in a complex power domain variously transitioning between a plurality of power states. The processor core includes a local context storage area for storage and retrieval of processor core context information. A low power context storage resides in a nominal power domain external to the complex power domain. Context information of the processor core is stored to the low power context storage based on whether a power state transition of the complex power domain includes a transition to power down the processor core.

What is claimed is: 
     
       1. A method comprising:
 detecting a first power state transition of a first power domain including a processor core; 
 in response to the detecting the first power state transition, sending from the processor core a query to determine whether the first power state transition is to include a transition to a first power state of a plurality of power states of the first power domain, wherein the first power state includes a state in which the processor core is powered down; and 
 in response to determining that the first power state transition is to include the transition to the first power state, saving context information of the processor core in a first context storage, otherwise, saving the context information in a second context storage. 
 
     
     
       2. The method of  claim 1 , wherein the first context storage and the second context storage include a static random access memory (SRAM). 
     
     
       3. The method of  claim 1 , wherein saving the context information in the first context storage includes:
 saving the context information to the second context storage, and 
 copying the context information saved in the second context storage to the first context storage. 
 
     
     
       4. The method of  claim 1 , wherein saving the context information in the first context storage includes saving without accessing the second context storage. 
     
     
       5. The method of  claim 1 , wherein the first context storage is in a second power domain separate from the first power domain, wherein a power state of the second power domain includes a power characteristic maintained during each of the plurality of power states of the first power domain. 
     
     
       6. The method of  claim 5 , wherein the power characteristic includes the first context storage being provided at least a first supply voltage level. 
     
     
       7. The method of  claim 1 , further comprising
 detecting an indication of a second power state transition of the first power domain, the second power state transition subsequent to the first power state transition; 
 in response to the detecting the indication of the second power state transition, determining whether the second power state transition includes a transition from the first power state; and 
 if the second power state transition is determined to include the transition from the first power state, then
 retrieving the context information from the first context storage, else 
 if the second power state transition is determined to not include the transition from the first power state, then retrieving the context information from the second context storage. 
 
 
     
     
       8. A system comprising:
 a processor device including a processor core, the processor core to detect a power state transition of a first power domain including the processor device, the processor core further to send a query from the processor core in response to the detecting the power state transition, the query to determine whether the power state transition includes a transition to a first power state of a plurality of power states of the first power domain, wherein the first power state includes a state in which the processor core is powered down; and 
 a second context storage device coupled to the processor device; 
 wherein the processor core to save context information of the processor core in the second context storage device in response to a determination that the power state transition includes the transition to the first power state, otherwise, the processor core to save the context information in a first context storage. 
 
     
     
       9. The system of  claim 8 , wherein the first context storage and the second context storage device include a static random access memory (RAM). 
     
     
       10. The system of  claim 8 , wherein the processor core to save the context information in the second context storage device includes:
 the processor core to save the context information to the first context storage, and 
 the processor core to copy the context information saved in the second context storage device to the first context storage. 
 
     
     
       11. The system of  claim 8 , wherein the second context storage device is in a second power domain separate from the first power domain, wherein a power state of the second power domain maintains a power characteristic during each of the plurality of power states plurality of power states of the first power domain. 
     
     
       12. An apparatus comprising:
 a processor core to detect a power state transition of a first power domain including the processor core, the processor core further to send a query from the processor core in response to the detecting the power state transition, the query to determine whether the power state transition includes a transition to a first power state of a plurality of power states of the first power domain, wherein the first power state includes a state in which the processor core is powered down; 
 wherein a second context storage is coupled to the processor core; 
 wherein the processor core to save context information of the processor core in the second context storage in response to a determination that the power state transition is to include the transition to the first power state, otherwise, the processor core to save the context information in a first context storage. 
 
     
     
       13. The apparatus of  claim 12 , wherein the first context storage and the second context storage include a static random access memory (RAM). 
     
     
       14. The apparatus of  claim 12 , wherein the processor core to save the context information in the second context storage includes:
 the processor core to save the context information to the first context storage, and 
 the processor core to copy the context information saved in the second context storage to the first context storage. 
 
     
     
       15. The apparatus of  claim 12 , wherein the second context storage is in a second power domain separate from the first power domain, wherein a power state of the second power domain provides a power characteristic during each of the plurality of power states plurality of power states of the first power domain.